共查询到20条相似文献,搜索用时 31 毫秒
1.
Matsuda R Anguizola J Joseph KS Hage DS 《Analytical and bioanalytical chemistry》2011,401(9):2811-2819
This study used high-performance affinity chromatography (HPAC) to examine the binding of gliclazide (i.e., a sulfonylurea
drug used to treat diabetes) with the protein human serum albumin (HSA) at various stages of modification due to glycation.
Frontal analysis conducted with small HPAC columns was first used to estimate the number of binding sites and association
equilibrium constants (K
a) for gliclazide with normal HSA and glycated HSA. Both normal and glycated HSA interacted with gliclazide according to a
two-site model, with a class of high-affinity sites (average K
a, 7.1–10 × 104 M−1) and a group of lower-affinity sites (average K
a, 5.7–8.9 × 103 M−1) at pH 7.4 and 37 °C. Competition experiments indicated that Sudlow sites I and II of HSA were both involved in these interactions,
with the K
a values for gliclazide at these sites being 1.9 × 104 and 6.0 × 104 M−1, respectively, for normal HSA. Two samples of glycated HSA had similar affinities to normal HSA for gliclazide at Sudlow
site I, but one sample had a 1.9-fold increase in affinity at this site. All three glycated HSA samples differed from normal
HSA in their affinity for gliclazide at Sudlow site II. This work illustrated how HPAC can be used to examine both the overall
binding of a drug with normal or modified proteins and the site-specific changes that can occur in these interactions as a
result of protein modification. 相似文献
2.
Contracted Gaussian-type function (CGTF) basis sets are reported for valence p orbitals of the six alkali and alkaline-earth atoms Li, Be, Na, Mg, K, and Ca for molecular applications. These sets are
constructed by Roothaan–Hartree–Fock calculations for the ns → np excited states of atoms, in which both linear and nonlinear parameters of CGTFs are variationally optimized. The present
CGTF sets reproduce well the numerical Hartree–Fock ns → np excitation energies: the largest error is 0.0009 hartrees for Li. New CGTFs are tested with diatomic Li2, Na2, K2, and MH molecules, where M = Li, Be, Na, Mg, K, and Ca, by self-consistent-field (SCF) and multiconfiguration SCF calculations.
The resultant spectroscopic constants compare well with those of more elaborate calculations and are sufficiently close to
experimental values, supporting the efficiency of the present set for the valence p orbitals.
Received: 9 July 1998 / Accepted: 17 September 1998 / Published online: 1 February 1999 相似文献
3.
A sequence-ordered, periodic copolymer of ethylene, ethylene, and acrylic acid, poly (ethylene-per-ethylene-per-acrylic acid) (PEEA), with M
w=1.44×105 has been synthesized by alternating copolymerization of 1,3-butadiene and methyl acrylate, followed by hydrogenation and
hydrolysis. Aqueous solution and dissociation properties of the alkali-soluble PEEA were explored by potentiometric titration
and intrinsic viscosity at 25 °C. The pH values of PEEA were almost constant (pH = 6.48 ∼ 6.55) with an increasing degree
of dissociation (α) from 0.3 to 0.8 at C
s=50 mN NaCl. Correspondingly, the plots of negative logarithm of apparent dissociation constant (pK
a) against α showed a reversed S-shape curve over the whole α, indicating an extensive precipitation and subsequent tran-sition
from compact to coiled conformation. The intrinsic viscosity steeply increased with α above 0.4 up to 9.97 dl/g at α = 1.0.
Good agreement between the observed electrostatic potential and that calculated from the rod model with a smeared charge density
was observed in the region of α higher than 0.9. The dissociation and dissolution processes of PEEA with neutralization in
water were described.
Received: 14 April 1998 Accepted: 3 June 1998 相似文献
4.
Jana Ehlerova Liliana Trevani Josef Sedlbauer Peter Tremaine 《Journal of solution chemistry》2008,37(6):857-874
The UV-visible spectra of aqueous o-, m-, and p-nitrophenol were measured as a function of pH at temperatures from 50 to 225 °C at a pressure of 7 MPa. These were used to
determine equilibrium constants for the acid ionization reaction of each isomer. The new results were combined with literature
data on the ionization of nitrophenols and used for parameter optimization in the thermodynamic model of Marshall and Franck
(J. Phys. Chem. Ref. Data 10:295–304, [1981]), to describe the dependence of ionization properties on temperature and pressure. The model yields predictions of the ionization
constants for o-, m-, and p-nitrophenol, log 10
K
a, to at least 250 °C and 20 MPa with an estimated uncertainty in log 10
K
a of less than ±0.06. 相似文献
5.
Rabindra N. Roy Lakshmi N. Roy Michael S. Fuge Chandra N. Roy Curtis A. Himes Paul A. Bryant Kyle T. Robinson Daniel A. Kaufmann II Colby H. Grove Toshi Gosh Adonis Bwashi 《Journal of solution chemistry》2009,38(4):471-483
The values of the second dissociation constant, pK
2, and related thermodynamic quantities of [N-(2-acetamido)-2-aminoethanesulfonic acid] (ACES) have already been reported over
the temperature range 5 to 55 °C including 37 °C. This paper reports the pa
H values of four chloride ion free buffer solutions and eight buffer solutions with I=0.16 mol⋅kg−1, matching closely that of the physiological sample. Conventional pa
H values for all twelve buffer solutions from 5 to 55 °C are reported. The residual liquid-junction potential correction for
two widely used temperatures, 25 and 37 °C, has been made. The flowing-junction calomel cell method has been utilized to measure
E
j
, the liquid-junction potential. The operational pH values for four buffer solutions at 25 and 37 °C are calculated using
the physiological phosphate buffer standard based on the NBS/NIST convention. These solutions are recommended as pH standards
in the pH range of 6.8 to 7.2 for physiological fluids. 相似文献
6.
Han Woong Park Hye-Seung Jin Sung Yun Yang Jong-Duk Kim 《Colloid and polymer science》2009,287(8):919-926
New pH-sensitive graft copolymers based on poly(2-hydroxyethyl aspartamide) (PHEA) were prepared by attaching various cationic
monomers, such as 4-(aminomethyl)pyridine (PY), 1-(3-aminopropyl)imidazole (IM), and N-(3-aminopropyl)dibuthylamine (BU), as pH-sensitive units and octadecylamine (C18) as a hydrophobic segment on poly(succinimide). Phase transition of each copolymer solution occurred at a vicinity of the
pK
a
value of the cationic groups, and their insoluble pH ranges were broadened as the feed amount of pH-sensitive moieties was
increased. Depending on the cationic grafts having different pK
a
values, the pH ranges where the copolymer became insoluble could be tuned. Copolymers PHEA-g-C18-PY, PHEA-g-C18-IM, and PHEA-g-C18-BU exhibited phase separations in solutions at pH ranges of 4∼6, 6∼8, and 9∼12, respectively. These polymers have the unique
feature of their pH sensitivity profiles being identified to three regimes. Under low pH conditions (below pK
a
), the polymer solution is transparent. At medium pH (around pK
a
), polymer precipitation occurred in solution. At pH > pK
a
, the polymer solution is gradually dissolved again. 相似文献
7.
N. N. Basargin E. R. Oskotskaya I. N. Senchakova Yu. G. Rozovskii 《Russian Journal of Inorganic Chemistry》2009,54(10):1619-1624
Physicochemical properties of new reagents, azo-substituted pyrocatechol derivatives and their tin(II) complexes, are studied.
The acid-base properties of the hydroxy groups (pK′i, pK″i), parameters of complex formation reactions (pH, temperature, time), and instability constants of the complexes formed (pK
i) are determined. Quantitative correlations between the dissociation constants (pK′a) of the functional analytical group, and the electronic Hammett constant σ for a substituent (pK′a-pH50 of the complex formation reaction), as well as between pK′a and instability constants of the complexes (pK
a), are established. The quantitative correlations established allow the prediction of the physicochemical properties of the
reagents and tin(II) complexes with new reagents of this class with the same functional analytical group (FAG) but other substituents. 相似文献
8.
Ramešová S Sokolová R Degano I Bulíčková J Zabka J Gál M 《Analytical and bioanalytical chemistry》2012,402(2):975-982
The natural flavonoid compounds quercetin (3,3′,4′,5,7-pentahydroxyflavone) and luteolin (3′,4′,5,7-tetrahydroxyflavone) are
important bioactive compounds with antioxidative, anti-allergic, and anti-inflammatory properties. However, both are unstable
when exposed to atmospheric oxygen, which causes degradation and complicates their analytical determinations. The oxidative
change of these flavonoids was observed and followed by UV–visible spectrophotometry, both in aqueous and ethanolic solutions.
The distribution of the degradation products in aqueous media was monitored by LC–MS and LC–DAD analysis. The amounts of oxidative
reaction products increase with the exposure time. The oxidative degradation reduces the pharmacological efficiency of these
antioxidants and renders analytical determination inaccurate. The oxidative changes in flavonoid test solutions can explain
the inconsistent dissociation constants reported in the literature. Dissociation constants of quercetin and luteolin were
determined both by alkalimetric titration and by UV–visible spectrophotometry under deaerated conditions. The values pK
1 = 5.87 ± 0.14 and pK
2 = 8.48 ± 0.09 for quercetin, and pK
1 = 5.99 ± 0.32 and pK
2 = 8.40 ± 0.42 for luteolin were found. 相似文献
9.
Maria das Graças Nunes Matos Vivian Gouveia Diniz Cesar Augusto Moraes de Abreu Augusto Knoechelmann Valdinete Lins da Silva 《Adsorption》2009,15(1):75-80
Heavy metals can be removed from effluents and recovered using physico-chemical mechanisms as biosorption processes. In this
work “Arribada” seaweed biomass was employed to assess its biosorptive capacity for the chromium (Cr3+) and lead (Pb2+) cations that usually are present in waste waters of plating industries. Equilibrium and kinetic experiments were conducted
in a mixed reactor on a batch basis. Biosorption equilibrium and fluid-solid mass transfer constants data were analyzed through
the concept of ion exchange sorption isotherm. The respective equilibrium exchange constants (K
eqCr=173.42, K
eqPb=58.86) and volumetric mass transfer coefficients ((k
mCr
a)′=1.13×10−3 s−1, (k
mPb
a)′=0.89×10−3 s−1) were employed for the dynamic analysis of Cr and Pb sorption in a fixed-bed flow-through sorption column. The breakthrough
curves obtained for both metals were compared with the predicted values by the heterogeneous model (K
eqCr=171.29, K
eqPb=60.14; k
mCr
a=7.81×10−2 s−1, k
mPb
a=2.43×10−2 s−1), taking into account the mass transfer process. The results suggest that these algae may be employed in a metal removal/recovery
process at low cost.
An erratum to this article can be found at 相似文献
10.
Lakshmi N. Roy Rabindra N. Roy Sean R. LeNoue Cole E. Denton Michael S. Fuge Craig D. Dunseth Chandra N. Roy Shawn M. Hayden Joshua T. Wollen Kripa Sreepada 《Journal of solution chemistry》2009,38(4):459-469
The values of the second dissociation constant, pK
2, and related thermodynamic quantities of 3-[N,N-bis (2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid (DIPSO) have already
been reported over the temperature range 5 to 55 °C including 37 °C. This paper reports the pH values of four NaCl-free buffer
solutions and four buffer composition containing NaCl salt at I=0.16 mol⋅kg−1. Conventional pa
H values are reported for all eight buffer solutions. The operational pH values have been calculated for four buffer solutions
recommended as pH standards, at 25 and 37 °C after correcting the liquid junction potentials with the flowing junction cell. 相似文献
11.
Franz Pertlik 《Monatshefte für Chemie / Chemical Monthly》2001,132(12):1509-1513
Summary. Single crystals of K2Ag12Te7 (a = 11.460(2), c = 4.660(1) ?; V = 530.01 ?3; space group: P63/m; Z = 1) were synthesized under hydrothermal conditions at 250°C in concentrated aqueous KOH solution from elementary silver
and tellurium. The crystal structure is characterized by trigonal prismatic KTe6 polyhedra, connected via two common faces to KTe3 rods parallel to [001]. These rods are combined by two crystallographically independent Ag atoms, each coordinated to four
Te and three Ag atoms (Ag–Te and Ag–Ag < 3.1 ?) to a framework of the formula (K2Ag12Te6)2 + and with channels parallel to the sixfold axis. These channels are statistically occupied by one further Te atom per unit
cell, distributed over two independent positions.
Received May 17, 2001. Accepted (revised) July 3, 2001 相似文献
12.
Franz Pertlik 《Monatshefte für Chemie / Chemical Monthly》2001,33(4):1509-1513
Single crystals of K2Ag12Te7 (a = 11.460(2), c = 4.660(1) ?; V = 530.01 ?3; space group: P63/m; Z = 1) were synthesized under hydrothermal conditions at 250°C in concentrated aqueous KOH solution from elementary silver and tellurium. The crystal structure is characterized by trigonal prismatic KTe6 polyhedra, connected via two common faces to KTe3 rods parallel to [001]. These rods are combined by two crystallographically independent Ag atoms, each coordinated to four Te and three Ag atoms (Ag–Te and Ag–Ag < 3.1 ?) to a framework of the formula (K2Ag12Te6)2 + and with channels parallel to the sixfold axis. These channels are statistically occupied by one further Te atom per unit cell, distributed over two independent positions. 相似文献
13.
Manabu Sugimoto Ichiro Yamasaki Nobuteru Mizoe Masaharu Anzai Shigeyoshi Sakaki 《Theoretical chemistry accounts》1999,102(1-6):377-384
Acetylene insertion into Pt(II)–H and Pt(II)SiH3 bonds of PtH(SiH3)(PH3) was investigated using ab initio molecular orbital and M?ller-Plesset perturbation theory methods. The insertion into PtH
was predicted to proceed with a smaller activation energy (E
a
=12.8 kcal/mol) than that into PtSiH3 (E
a
=20.9 kcal/mol). The reaction energy (ΔE) of the insertion into PtH is 10 kcal/mol smaller than that for the insertion into PtSiH3, which reflects differences in bond energies between CH and CSi and between PtH and PtSiH3. A comparison with ethylene insertion revealed that the acetylene insertion occurs more easily, and the latter reaction is
more exothermic. A simple vibronic coupling model combined with Toyozawa's interaction mode analysis was used to examine interesting
differences in E
a
and ΔE between insertions into PtH and PtSiH3, and between acetylene and ethylene insertions. This analysis suggests that the factors determining E
a
are the stiffness of the PtH and PtSiH3 bonds and the vibronic coupling strength of acetylene and ethylene.
Received: 13 August 1998 / Accepted: 2 September 1998 / Published online: 15 February 1999 相似文献
14.
Kenzi Hori Nobuhisa Saitoh Shinjiro Kobayashi Tsugio Kitamura 《Theoretical chemistry accounts》1999,102(1-6):244-251
β, γ-Substituted γ-halo allylalkoxide ions decompose to form a halogen ion, formaldehyde, and an alkyne under mild conditions,
for example at room temperature. The E isomer does not differ from the Z isomer in terms of activation energy. We attempted
to shed light on the mechanism of the reaction by using ab initio molecular orbital calculations. The observed propensity
was confirmed by the present calculation on model molecules, γ-chloro allylalkoxide ions. We conducted further calculations
and compared the alkoxide results with a similar reaction of β-haloacrylate ions that release carbon dioxide instead of formaldehyde.
This similar reaction needs heating as high as 150°C. The activation energy of the acrylate ions (36–39 kcal mol−1) was calculated to be about 10 kcal mol−1 higher than that of the alkoxide ions. The activation energy of the E acrylate ion is smaller by 0.8 kcal mol−1 than that of the Z isomer at the MP2/6-31+G**//RHF/6-31+G* level of theory. This is consistent with experimental results.
While the ready deprotonation from the carboxylic group does not activate the acrylate ion very much, the alkoxide ion is
destabilized to a great degree in the process of anion formation. The difficulty in deprotonation that proceeds from the neutral
molecule is seen in the difference in the activation energies for the decomposition of the corresponding anions. Therefore,
the pK
a of a hydroxy or a carboxylic group plays the leading role in determining the magnitude of activation energies of allyl halides
with a negatively charged fragment.
Received: 2 July 1998 / Accepted: 9 September 1998 / Published online: 8 February 1999 相似文献
15.
Ivan Kron Zuzana Pudychová-Chovanová Beáta Veliká Juraj Guzy Pál Perjési 《Monatshefte für Chemie / Chemical Monthly》2012,181(6):13-17
Abstract
UV–Vis spectrophotometry was used to determine acid dissociation constant (pK a) values of the natural flavonoids phloretin, phlorizin, naringenin, and naringin, as well as 4′-hydroxychalcone, 4′-(dimethylamino)chalcone, and their cyclic analogues. Comparison of the results with those previously reported for the natural flavonoids showed the applied method is a relatively straightforward and easy-to-perform technique for the determination of pK a values of compounds with relatively low solubility. Comparative analysis of the pK a values of the synthetic chalcones showed a strong correlation between the degree of conjugation and the acid strength of the respective compounds with different geometry. Our results provide further evidence that modification of the three-dimensional structure of open-chain bioactive compounds is the method of choice to modify not only their stereochemistry but also their physicochemical properties. 相似文献16.
Effect of pH and ionic strength on the interaction of humic acid with aluminium oxide 总被引:4,自引:0,他引:4
E. Tombácz Á. Dobos M. Szekeres H. D. Narres E. Klumpp I. Dékány 《Colloid and polymer science》2000,278(4):337-345
The effect of pH and neutral electrolyte on the interaction between humic acid/humate and γ-AlOOH (boehmite) was investigated.
The quantitative characterization of surface charging for both partners was performed by means of potentiometric acid–base
titration. The intrinsic equilibrium constants for surface charge formation were logK
a,1
int=6.7±0.2 and logK
a,2
int = 10.6±0.2 and the point of zero charge was 8.7±0.1 for aluminium oxide. The pH-dependent solubility and the speciation of
dissolved aluminium was calculated (MINTEQA2). The fitted (FITEQL) pK values for dissociation of acidic groups of humic acid were pK
1 = 3.7±0.1 and pK
2 = 6.6±0.1 and the total acidity was 4.56 mmol g−1. The pH range for the adsorption study was limited to between pH 5 and 10, where the amount of the aluminium species in the
aqueous phase is negligible (less than 10−5 mol dm−3) and the complicating side equilibria can be neglected. Adsorption isotherms were determined at pH ∼ 5.5, ∼8.5 and ∼9.5,
where the surface of adsorbent is positive, neutral and negative, respectively, and at 0.001, 0.1, 0.25 and 0.50 mol dm−3 NaNO3. The isotherms are of the Langmuir type, except that measured at pH ∼ 5.5 in the presence of 0.25 and 0.5 mol dm−3 salt. The interaction between humic acid/humate and aluminium oxide is mainly a ligand-exchange reaction with humic macroions
with changing conformation under the influence of the charged interface. With increasing ionic strength the surface complexation
takes place with more and more compressed humic macroions. The contribution of Coulombic interaction of oppositely charged
partners is significant at acidic pH. We suppose heterocoagulation of humic acid and aluminium oxide particles at pH ∼ 5.5
and higher salt content to explain the unusual increase in the apparent amount of humic acid adsorbed.
Received: 20 July 1999 /Accepted in revised form: 20 October 1999 相似文献
17.
Jaakko I. Partanen Pekka M. Juusola Arthur K. Covington 《Journal of solution chemistry》2009,38(11):1385-1416
Equations were developed for the calculation of the first stoichiometric (molality scale) dissociation constant (K
m1) of oxalic acid in buffer solutions containing oxalic acid, potassium hydrogen oxalate, and potassium chloride from the determined
thermodynamic values of this dissociation constant (K
a1) and the molalities of the components in the solutions. Similar equations were also developed for the second stoichiometric
dissociation constant (K
m2) of this acid in buffer solutions containing sodium or potassium hydrogen oxalate, oxalate and chloride. These equations
apply at temperatures from 0 to 60 °C up to ionic strengths of 1.0 mol⋅kg−1 and they have been based on single-ion activity coefficient equations of the Hückel type. For the equations for K
m1, the activity parameters of oxalate species and the K
a1 values were determined at various temperatures from the Harned cell data of a recent tetroxalate buffer paper (Juusola et
al., J. Chem. Eng. Data 52:973–976, 2007). By using the resulting equations for K
m1, the activity parameters of oxalate species for K
m2 and the K
a2 values were then determined from the new Harned cell data and from those of Pinching and Bates (J. Res. Natl. Bur. Stand.
(U.S.) 40:405–416, 1948) for solutions of sodium or potassium oxalates with NaCl or KCl. The resulting simple equations for calculation of K
m1 and K
m2 for oxalic acid were tested with all important thermodynamic data available in the literature for this purpose. The equations
for ln (K
a1) and ln (K
a2) are of the form ln (K
a)=a+b(t/°C)+c(t/°C)2. The coefficients for ln (K
a1) are the following: a=−2.8737, b=0.000159, and c=−0.00009. The corresponding coefficients for ln (K
a2) are −9.6563, −0.003059, and −0.000125, respectively. The new activity coefficient equations were used to evaluate the pH
values of the tetroxalate buffer solution (i.e., of the 0.05 mol⋅kg−1 KH3C4O8 solution) for comparison with the pH values recommended by IUPAC at temperatures from 0 to 60 °C and to develop a new two-component
oxalate pH buffer of 0.01 mol⋅kg−1 KHC2O4+0.05 mol⋅kg−1 Na2C2O4 for which pH values are given from 0 to 60 °C. Values of p(m
H) calculated from these equations are tabulated for these buffers as well as for buffer solutions with KCl and KH3C4O8 as the major component and minor component, respectively. Tables of p(m
H) are also presented for 0.001 mol⋅kg−1 KHC2O4+0.005 mol⋅kg−1 Na2C2O4 solutions in which KCl is the supporting electrolyte. 相似文献
18.
Javed MR Rashid MH Nadeem H Riaz M Perveen R 《Applied biochemistry and biotechnology》2009,157(3):483-497
Monomeric extracellular endoglucanase (25 kDa) of transgenic koji (Aspergillus oryzae cmc-1) produced under submerged growth condition (7.5 U mg−1 protein) was purified to homogeneity level by ammonium sulfate precipitation and various column chromatography on fast protein
liquid chromatography system. Activation energy for carboxymethylcellulose (CMC) hydrolysis was 3.32 kJ mol−1 at optimum temperature (55 °C), and its temperature quotient (Q
10) was 1.0. The enzyme was stable over a pH range of 4.1–5.3 and gave maximum activity at pH 4.4. V
max for CMC hydrolysis was 854 U mg−1 protein and K
m was 20 mg CMC ml−1. The turnover (k
cat) was 356 s−1. The pK
a1 and pK
a2 of ionisable groups of active site controlling V
max were 3.9 and 6.25, respectively. Thermodynamic parameters for CMC hydrolysis were as follows: ΔH* = 0.59 kJ mol−1, ΔG* = 64.57 kJ mol−1 and ΔS* = −195.05 J mol−1 K−1, respectively. Activation energy for irreversible inactivation ‘E
a(d)’ of the endoglucanase was 378 kJ mol−1, whereas enthalpy (ΔH*), Gibbs free energy (ΔG*) and entropy (ΔS*) of activation at 44 °C were 375.36 kJ mol−1, 111.36 kJ mol−1 and 833.06 J mol−1 K−1, respectively. 相似文献
19.
A 66-kDa thermostable family 1 Glycosyl Hydrolase (GH1) enzyme with β-glucosidase and β-galactosidase activities was purified
to homogeneity from the seeds of Putranjiva roxburghii belonging to Euphorbiaceae family. N-terminal and partial internal amino acid sequences showed significant resemblance to plant GH1 enzymes. Kinetic
studies showed that enzyme hydrolyzed p-nitrophenyl β-d-glucopyranoside (pNP-Glc) with higher efficiency (K
cat/K
m = 2.27 × 104 M−1 s−1) as compared to p-nitrophenyl β-d-galactopyranoside (pNP-Gal; K
cat/K
m = 1.15 × 104 M−1 s−1). The optimum pH for β-galactosidase activity was 4.8 and 4.4 in citrate phosphate and acetate buffers respectively, while
for β-glucosidase it was 4.6 in both buffers. The activation energy was found to be 10.6 kcal/mol in the temperature range
30–65 °C. The enzyme showed maximum activity at 65 °C with half life of ~40 min and first-order rate constant of 0.0172 min−1. Far-UV CD spectra of enzyme exhibited α, β pattern at room temperature at pH 8.0. This thermostable enzyme with dual specificity
and higher catalytic efficiency can be utilized for different commercial applications. 相似文献
20.
We proposed basic principles for biosolvent design on the viewpoint of ionization. Two classes of biosolvents, based on cyclic
carbonate moiety and amide moiety, were designed through hydroxyl functionalization of highly dielectric compound. The newly
designed compounds, glycerol carbonate (GC) and N-hydroxymethyl formamide (HOF), were synthesized for the development of soluble
enzymatic systems and characterized by 13C NMR and 1H NMR. All the characterization data were consistent with the expected structures. Using conductance measurements, the pK
a values of trichloroacetic acid in GC and HOF were determined as 0.80 and 0.85 at 25.0 °C, which was very close to that in
water (pK
a = 0.70), suggesting that the ionizing and dissociating abilities of GC and HOF are similar to those of water. The effects
of various reaction parameters on activity and stability of Candida antarctica lipase B and lipase from Pseudomonas cepacia were investigated using the transesterification of ethyl butyrate with n-butanol as a model reaction. The activities of lipases
in GC and HOF were comparable to those in water, indicating that the newly designed compounds were biocompactible. Biosolvent
design is a promising and versatile method for developing new biosolvents. 相似文献